If you ask me, the most interesting question is "So how does this thing actually work?" And the answer according to engadget is "PCM is based on a special alloy that can be nudged into different physical states, or phases, by controlled bursts of electricity", or in other words "Fuck, I don't know, I didn't really understand the press release"

The press release is more informative. You put some undisclosed material between two electrodes. The material can be crystalline or amorphous, and you can tell which it is at any given time by the resistance. To change it from one to the other you simply heat it up with a voltage pulse to one threshold temperature or another. Neato!